Ball bearing assembly and loading apparatus



1964 M. A. SCHOOS BALL BEARING ASSEMBLY AND LOADING APPARATUS 2Sheets-Sheet 1 Original Filed Oct. 23, 1959 FIG. I

INVENTOR. MAURICE A. SCHOOS M. A. SCHOOS BALL BEARING ASSEMBLY ANDLOADING APPARATUS Original Filed Oct. 23, 1959 2 Sheets-Sheet 2 FIG. 3

FIG. 4

INVENTOR. MAURICE A. SCHOOS ATTORNEYS United States Patent 3,116,543BALL BEARING ASSEMBLY AND LOADING APPARATUS Maurice A. Schoos, Warwick,R.I., assignor to Kenney Manufacturing Company, Cranston, R.I., acorporation of Rhode Island Original application Oct. 23, 1959, Ser. No.848,262, now Patent No. 3,034,839, dated May 15, 1962. Divided and thisapplication Nov. 17, 1960, Ser. No. 69,993 1 Claim. (Cl. 29-201) Thisinvention relates to frictionless bearings and more particularlycomprises improvements in the method of making ball bearing assembliesfabricated, at least in part, by resilient rigid plastic materials,particularly the fiberforming crystalline high polymers such as nylon.This invention also includes a novel apparatus useful for as semblingthe improved bearing.

Low cost, light load ball bearing assemblies are presently in greatdemand for a large number of different applications. Bearing assembliesin which either or both races are fabricated from self-lubricatingplastic materials are particularly useful in pulleys for traverse rodassemblies, rollers for cabinet drawers, idler pulleys for movieprojectors as well as for a great many other uses.

Under present practice it is the custom for at least one of the plasticraces of such hearings to be made in two or more parts. The inner racemay be of one piece with the outer race made up of two or more partsthat are adapted to engage with one another over the inner race. Theouter race in such case may take the form of a standard race bisectedeither axially or in a plane normal to the race axis. Once the balls arepositioned in the inner race groove the two parts of the outer race arebrought together and locked in place. The outer race parts may be fixedto one another by an adhesive, by heating the pieces to a temperaturehigh enough to cause fusion between them or by mechanical means. In anyevent the multiplicity of parts and the several assembly operationsrequired combine to increase the cost of pro ducing the bearing.

It is one object of the present invention to reduce the cost ofproducing bearings having plastic races. This ob ject is achieved byproviding a one-piece outer race member having sufiicient elasticity tobe pressed axially into position about a one-piece inner race memberhaving a proper charge of bearing balls disposed thereabouts.

Another object of this invention is to provide an inexpensive ballbearing assembly that is easily assembled and dependable in operation.This object is attained by molding both the inner and outer races from aselflubricating plastic material such as nylon, Teflon or the like. Whenthe races and the balls have been oriented they may be pressed intoengagement by an ordinary hydraulic press. Once this operation isfinished the assembling of the bearing is completed. As a feature ofthis invention the edges of the ball groove in the outer race arebeveled to eliminate any burring or flashing that might otherwise occurwhen the race is pressed past the balls.

Another feature of this invention relates to a novel apparatus which maybe used to facilitate assembly of the bearing parts.

These and other features and objects will become more readily apparentfrom a detailed description of a preferred embodiment of the inventiontaken together with the accompanying drawings in which:

FIG. 1 is a cross section of a pulley made in accord ance with theinvention and showing the parts arranged in a position just prior tobeing pressed together,

FIG. 2 is a view similar to FIG. 1 but showing the parts in assembledposition.

FIG. 3 is a cross sectional view in elevation of a load ing apparatus,and

FIG. 4 is similar to FIG. 3 but showing the apparatus in its assembledposition.

Referring now to the drawings, the reference charac ter 10 generallyindicates a bearing assembly which, in this embodiment, is in the formof a pulley such as may be used in a traverse rod for curtains anddrapes. The bearing assembly 10 comprises an annular inner ring or racemember 12, a plurality of bearing balls 14 and an annular outer ring orrace member 16. Preferably, both the inner and outer races are molded byan injection proc ess from nylon, Teflon or the like. These materialsare relatively resilient, hard, and characterized by a rather smoothwaxy surface suitable for use as a bearing material in that nolubrication is required and minimum wear is involved. The inner race 12is formed with an axial bore 18 to receive suitable supporting means. Arather deep, U-shaped ball groove or raceway 20 extends about thecircumference of the inner race 12 and substantially en closes the balls14 disposed therein. Standard steel bearing balls may be used and for a/4 inch diameter bear ing assembly, it has been found that nine .125"balls are sulficient.

The outer race member 16 is' formed with a rather shallow ball groove orraceway '22 about its inner pe ripheral portion. This groove 22 isarcurate in cross section but spans only a relatively small portion ofthe balls. An outer groove 24 is provided about the outer race when theassembly is to be used as a pulley. Various other configurations such asgear teeth or the like may be formed to suit particular applications.

Assembling of the bearing is achieved by locating the proper number ofbearing balls within the groove 20 (FIG. 1) and pressing the outer race16 axially over the inner race 12 and the balls until the parts snapinto the posi* tion shown in FIG. 2. As the outer race is being pushedpast the balls, its diameter must not expand beyond its elastic limit.Taking the difference between the outer diameter of the inner race withthe balls in place (A, FIG. 1) and the minimum diameter of the outerrace (B, FIG. 1) as the assembly clearance (CH-C FIG. 2), it isnecessary that this clearance be within the elastic limit of the outerrace to prevent its permanent enlargement or breakage during assembling.To ease the outer race over the balls the outer edges may be beveled at26. Because of the pressure created during the assembling operation theballs might wipe or permanently displace small portions of the innersurface of the outer race. Should these displaced portions form a ridgeor lip extending into the groove 22 the run of the balls and the freemove ment of the race would be impeded. To avoid any such occurrence theedge of the groove 22 is beveled as at 28. This beveled edge completelyeliminates the problem, for whatever ridge is created during assemblingwill not be in a location that will interfere with the operation of thebearing.

A bearing of the type described is extremely easy and inexpensive tomanufacture. Although the races are preferably formed by a moldingprocess other methods such as machining or the like may also be used toadvantage.

By forming the groove 20 relatively deep in relation to the groove 22the inside diameter of the outer race will be of a dimension which willpermit it to be pressed axial- 1y into place without exceeding theelastic limit of the outer race member. Also the annular space betweenthe races is kept as narrow as possible to prevent the entry of lint anddust.

In View of the fact that both races \are one piece affairs at least oneassembly operation has been eliminated since there is no need to engagea locking member or to otherwise fasten together parts of a race as wasformerly the case.

Although the inner race has been described as fabricated from the samematerial as the outer race member it is by no means critical that it beso. Metal, wood, glass or other materials may be substituted for theplastic material described. However, it has been found that nylon ispreferable from the standpoint of economy, dependability and because ofits lubricating characteristics.

In FIGS. 3 and 4 there is illustrated an apparatus which may be used topress the outer race Hover the inner race 12 and the balls 14. Theapparatus shown herein cornprises a support 30* having an upwardlyprojecting cylindrical post 32 mounted thereon. An annular nest 34 ismounted for reciprocation about the post 32 and is normally urged to theupward position shown in FIG. 3 by a coil spring 36. A collar 38 fixedto the support 30 concentrically about the post 32 is provided withflanged portion 40 adapted to engage a shoulder 42 in the nest 34 tolimit the upward movement of the nest.

The upper portion of the post 32 is provided with a bifurcated collar 44projecting vertically upwards and is dimensioned to fit within the bore18 of the inner race and engage the walls thereof.

The nest 34 is provided about its upper portion with a well 46 slightlylarger in diameter than the outside diameter of the outer race 16 andhas vertical walls generally of the same height as the width of theouter race. As is clear from the drawing the lower portion of the well46 slopes towards the post 32 for the purpose which will be presentlyset forth.

In assembling the bearing in the loading apparatus, the inner race 12 isfirst deposited on the post 32 with the collet 44 snugly engaging thewalls of the bore 18. To accomplish this operation on a mass productionbasis the races may be introduced by a hopper fed chute with areciprocating plunger coaxially arranged with respect to the post 32 andadapted to push an inner race over the collet automatically.

Once an inner race 12 is in position a quantity of bearing balls 14 aremetered automatically into the well 46. The bottom portion of the well,being sloped, causes the balls to roll into their intended positions inthe groove 29.

In the next operation the outer race 16 is fed from chute 48 anddeposited in the well 46 by a plunger 50 (FIG. 3). At this point thebevel edge 26 of the outer race is resting on the balls 1-4 and assistsin holding the balls radially inward.

As seen in FIG. 4 a piston 52 is brought down upon the outer race andthe nest pressing them both simultaneously so as to snap the outer raceover the balls into position and to push the nest clear. For a bearinghaving the dimensions and materials described above a pressure of 200psi. is required against the outer race. When the pressure is releasedand the piston Withdrawn the spring l 36 will push the nest upwardsthereby stripping the assembled bearing 10 off the collet 44. A suitableautomatic pick-01f apparatus can be brought to bear to remove thehearing from the nest.

Although the invention has been described with particular reference to abearing in which a one-piece nylon outer race is pressed into assembledposition, it will be obvious to those skilled in the art that a greatmany modifications may be made to the invention. For instance, a widerange of materials may be substituted for the nylon specified herein.Also it may be desirable for some applications to provide a bearing inwhich the inner race is pressed into position rather than the outerrace. For such an embodiment the outer race would be provided with adeep ball groove and the inner race would have a shallow ball groovewith beveled edges. In any case it will be appreciated that the depth ofthe race is related to the modulus of elasticity of the particularplastic material such that in assembling the bearings the elastic limitis not exceeded. Also it may be desirable for some purposes tosubstitute needle or roller bearings for the ball bearings described.Many other modifications may be made both to the hearing and to theloading apparatus without departing from the spirit of the invention.

This application is a division of applicants co-pending application,Ser. No. 848,262, filed October 23, 1959, now Patent No. 3,034,839.

What I claim and desire to secure by Letters Patent of the United Statesis:

Apparatus for assembling a ball bearing comprising a support, acylindrical post vertically mounted on said support adapted to receiveand support an inner ball bearing race member, a reciprocable nestsurrounding said post and having a well formed in the upper portionthereof adapted to receive an outer ball bearing race member, a lowerportion of said well being inwardly sloped to direct balls toward saidinner race member, a reciprocable plunger movable vertically toward saidpost adapted to bear downwardly on said nest and an outer race memberthereon, thereby to force said outer race member about said inner racemember and to depress said nest, and means for raising said nest wherebythe assembled ball bearing is lifted by said nest from said post.

References Cited in the file of this patent UNITED STATES PATENTS941,632 Geschke Nov. 30, 1909 1,048,758 Sultemeyer Dec. 31, 19121,074,228 Whitney Sept. 30, 1913 1,153,066 Gurney Sept. 7, 19151,401,680 Dleak Dec. 27, 1921 2,702,216 Stearns Feb. 15, 1955

